The present invention relates to the use of epidermal growth factor (EGF) as a gastrointestinal therapeutic agent. In particular, EGF can be used to promote weight gain and prevent gastrointestinal colonization by pathogens. EGF may also be used to increase absorption of immunoglobulins. The inhibition of the EGF signalling cascade may be used to prevent uptake of toxic or adverse compounds as well as to promote weight loss.
A number of intestinal growth factors accelerate epithelial maturation and renewal. One of these is epidermal growth factor (EGF), a small acid stable gastrointestinal peptide that is naturally present in salivary and intestinal secretions and other body fluids, and is produced in large quantities in colostrum and milk. EGF promotes a) the proliferation and differentiation of intestinal cells during early life, b) the functional maturation of the pre-weaning intestine, and c) epithelial proliferation in the adult gut (10, 11, 12, 13, 14). Moreover, EGF acutely (within minutes) upregulates small intestinal absorption of electrolytes and nutrients, an effect which was shown to be related to a concurrent lengthening of the apical microvilli of enterocytes (15). Potential therapeutic benefits of EGF have been highlighted in studies where topical treatment with EGF promoted wound healing (30) and, more recently, by the observation that administration of EGF enhances nutrient absorption in remnant intestine following massive resection (16). Compared with the small intestine, more receptors for EGF are found in the colon (17), where the heaviest bacterial load is observed during infection with microorganisms such as Esherichia coli. EGF upregulates function in the entire intestine, including the colon (12, 16).
While EGF has been reported to have a variety of functions, its role in preventing intestinal colonization by pathogens or in accelerating weight gain have not been previously reported. These two newly discovered properties of EGF make it extremely useful as a therapeutic agent. The ability of EGF to prevent intestinal colonization or infection by pathogens has many important therapeutic applications. One such application is in the treatment of enteric colibacillosis in young farm animals.
Enteric colibacillosis is a bacterial infection with considerable implications for the economy of the agricultural industry. Enteric colibacillosis (also called scours) is one of the most common diseases of newborn and young farm animals (1-6). The microbe responsible for the disease is the pathogenic bacterium Escherichia coli (E. coli). The infection occurs wherever farm animals are maintained and is a significant cause of economic loss in Western Canada and other parts of the world. The disease is characterized by diarrhea, dehydration and eventual death. Therefore, there is a real need to develop a method to prevent the economic loss caused by enteric colibacillosis.
In addition to treating enteric colibacillosis in young farm animals, EGF can also be used to treat or prevent any condition that results from intestinal colonization by a pathogen, i.e. a virus (for example coronavirus, parvovirus rotavirus), a bacterium (for example Salmonella sp. and Shigella sp.) or a parasite (for example Cryptospordium sp. and Eimeria sp.) and traveller""s diarrhea. Another important use of EGF is in the prevention of bacterial colonization at gastric ulcer sites. It is now well documented that infection by the bacteria Helicobacter pylori is a major risk factor for recurrent peptic ulcer disease. It has been shown that bacterial colonization occurs at the ulcer site and contributes to the chronicity of the ulcer. Therefore, EGF may be useful in preventing colonization of the bacteria Helicobacter pylori and therefore may be useful in accelerating healing of gastric ulcers.
In addition to demonstrating that administration of EGF can prevent intestinal colonization by pathogens, the inventors have also shown that EGF can enhance weight gain in animals. The latter effect is unexpected as certain publications have indicated that EGF has no effect on weight gain (21, 25). Other studies investigating the effects of EGF in pigs (28, 29) were unable to demonstrate an acceleration in growth rate, despite concurrent increases in the levels of intestinal disaccharidases.
The use of EGF in accelerating weight gain also has many important therapeutic applications. This property is useful when treating intestinal infection especially where weight loss from diarrhea and dehydration accompanies the infection. This property is also useful in increasing production in the animal industry such as in the beef, pig, poultry and fish industry. The latter industry is becoming more important as more fish are being produced through aquaculture. In the animal industry EGF can be easily administered as a food additive or in the drinking water of farm animals. The use of EGF to promote weight gain can also be used to treat malnourished people and persons suffering from anorexia nervosa.
In addition to preventing colonization by pathogens and increasing weight gain, EGF has also been shown to increase the intestinal absorption of nutrients. This property also has many therapeutic applications. For example, this property makes EGF more useful in treating intestinal infections or in promoting weight gain by increasing the absorption of nutrients that may be needed in such circumstances. Further, by upregulating gastrointestinal absorption, EGF may also increase immunoglobulin uptake in the newborn.
The major source of immunoglobulin for the newborn is maternal colostrum and milk, and failure to appropriately absorb maternal immunoglobulin correlates with high morbidity and mortality from infectious diseases (31). The rate of immunoglobulin absorption is greatest during the first days of life, after which immunoglobulin uptake decreases and gut closure occurs. Administration of EGF may (a) promote immunoglobulin absorption from colostrum, milk or other sources (such as oral immunoglobulin preparations) and (b) delay gut closure which may also enhance immunoglobulin uptake.
As discussed above, EGF causes an increase in the intestinal absorption of nutrients. Consequently, inhibition of the EGF signalling cascade reduces intestinal absorption of nutrients. The clinical benefits of inhibiting the EGF signalling cascade in the regulation of gastrointestinal nutrient absorption have never been assessed. It is predicted that antagonists of the EGF receptor or the EGF signalling cascade may be used as a gastrointestinal therapeutic agent where decreased intestinal absorption may be warranted for example in treating obesity, or to decrease intestinal uptake of toxic or adverse substances.
The present invention relates to the use of epidermal growth factor (EGF) as a gastrointestinal therapeutic agent.
In one aspect, the present invention provides the use of EGF to prevent or treat intestinal colonization by a pathogen in an animal. Intestinal infection and disease is the major cause of loss in food producing animals.
The term xe2x80x9canimalxe2x80x9d as used herein is meant to include all members of the animal kingdom such as fish and mammals (including farm animals and even humans).
The term xe2x80x9cpathogenxe2x80x9d as used herein is meant to include any organism capable of causing disease such as bacteria, viruses and parasites. Examples of bacterial pathogens that can invade the gastrointestinal system include E. coli and salmonella typhimurium. 
The EGF is preferably administered orally, for example in the feed of the animal. Further, lyophilized EGF added to drinking water has proven stable and therefore can be administered as such.
In one embodiment, the present invention provides the use of EGF to treat or prevent enteric infections (viral, bacterial or parasitic) in an animal.
In another embodiment, the present invention provides the use of EGF to treat or prevent enteric colibacillosis (scours) in an animal.
In a further embodiment, the present invention provides the use of EGF to prevent gastric ulcers or to accelerate the healing of gastric ulcers associated with Helicobacter pylori. 
In another aspect, the present invention provides the use of EGF to increase weight gain in an animal. This is useful in increasing production in the animal industry such as the agriculture industry and aquaculture industry where there is a demand for non-drug food additives that enhance production.
In a further aspect, the present invention the use of EGF to increase immunoglobulin absorption in the intestine of an animal, especially a newborn animal.
In yet a further aspect, the present invention provides the use of an agent that inhibits the activity of EGF to decrease intestinal absorption of nutrients. This may be useful in situations where decreased intestinal absorption is desired such as in treating obesity or in decreasing the intestinal absorption of toxins.
The present invention also includes within its scope the use of EGF to prepare a medicament to treat or prevent any of the conditions mentioned above.